1. Field of the Invention
The present invention relates to apparatuses for generating analog driving voltages and common electrode voltages and methods of controlling the analog driving voltages and the common electrode voltages.
2. Description of the Related Art
Generally, a liquid crystal display device includes a liquid crystal display panel for displaying images, a data driver for outputting an analog grayscale voltage to the liquid crystal display panel, a gate driver for outputting a gate driving signal through a plurality of gate lines to the liquid crystal display panel, a timing controller for outputting various timing control signals, a DC-to-DC converter, a grayscale voltage generating unit and a common electrode voltage generating unit.
The DC-DC converter receives a DC voltage from an external source and converts the DC voltage into an analog driving voltage (AVDD) for driving the data driver and the gate driver.
The AVDD voltage may be used to generate a gate turn-on voltage VON, a gate turn-off voltage VOFF and a grayscale reference voltage VDD. The gate driver outputs a plurality of gate driving signals through a plurality of gate lines to the liquid crystal display panel based on the gate turn-on voltage VON and the gate turn-off voltage VOFF. The grayscale voltage generating unit provides the grayscale reference voltage VDD to the data driver.
Meanwhile, the AVDD voltage has a considerable effect on the contrast ratio of a screen and a current consumption of the liquid crystal display panel.
Therefore, the analog driving voltage AVDD should be adjusted to an optimum AVDD voltage according to characteristics of loads in the liquid crystal panel, such as TFT transistors, capacitors, resistors, etc.
In addition, the common electrode voltage generating unit adjusts the common electrode voltage VCOM to a preset voltage to minimize flicker. However, differences between respective liquid crystal display devices or variation of the load characteristics of the liquid crystal panel cause variations in the common electrode voltage VCOM. Therefore, it is desirable to adjust the common electrode voltage VCOM to an appropriate voltage level for reducing flicker.